Current plastic insulation is a little thinner, but that looks about right. You just need to be sure you use a large enough junction box that is accessble to make the splice.

If you touch that at all, it can not be to extend it. You need to bring the whole circuit up to the modern code required 8/4. I’d personally do a 6/4, with a 40 amp breaker, in case you want to ditch the old fashioned electric for the modern standard of 50 amp induction.

That’s what I figured. Stupid old houses…. I don’t have it in me to run another wire! Haha. I’ll call around and get some quotes from local electricians. Thanks for your insight.

@User-- what is the 4th conductor used for in a single phase circuit? Agree that if there is no ground in the cable it needs to be upgraded and if you need to upgrade it. I'd also upsize to accomodate things like high amperage induction and bigger ovens. Don't see why the more typical 6-3 w/g NM-B wouldn't work, ie with three 6 ga conductors and a 10 g ground.

The third conductor in a 6-3 w/g NM-B cable is used as the neutral. The uninsulated, smaller gauge ground wire cannot be used as a conductor.